The catch
Blueair Blue Pure 311i Max
It isn't suitable if you insist on no ionizer, because HEPASilent leaves its ionization stage active.
Side by side
Blueair 311i Max vs Blueair 511i Max: 311i has more airflow, 511i takes less space in a small bedroom
Quick verdict
Go with the 311i Max for a shared room. If you don't need the larger airflow reserve, the 511i Max is easier to place in a small bedroom.
Before you buy
Why, and what it costs you
Compare room sizes at an equal turnover rate
Blueair 311i Max works out to about 425 square feet and Blueair 511i Max to 230, at five air changes per hour and an eight-foot ceiling.
Where this comes from
Area = CADR × 60 / (ceiling feet × air changes per hour). Inputs are 283 and 153 CFM, 8 feet and 5 changes. Smoke CADR is taken at maximum speed. Real conditions are affected by air mixing, furniture, open doors and filter loading.
The catch
Blueair Blue Pure 511i Max
The HEPASilent ionizer runs constantly and there is no way to disable it.
Blueair Blue Pure 311i Max
- Why pick it
- Airflow has to be stronger for a shared room
- Pollen throughput ranks high for you
- The catch
- It isn't suitable if you insist on no ionizer, because HEPASilent leaves its ionization stage active.
Blueair Blue Pure 511i Max
- Why pick it
- Only a small corner of floor is free
- A lighter unit suits daily moving
- The catch
- The HEPASilent ionizer runs constantly and there is no way to disable it.
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What this page compares
A shared room calls for the 311i Max. The 511i Max is easier to place in a small bedroom that doesn't need the larger airflow reserve.
Ceiling and room size outweigh the model number
Which one fits
Pick the situations that sound like you
The room is big enough to call for extra airflow
With the same five-change target and eight-foot ceiling, the calculated limits are 425 square feet for Blueair 311i Max and 230 for Blueair 511i Max. Allow margin for running below maximum speed.
- Blueair Blue Pure 311i Max
- Better fit
- Blueair Blue Pure 511i Max
- Depends
The cabinet needs to fit next to furniture
Set aside 12.5 inches of width and 12.5 inches of depth for Blueair 311i Max, or 9.3 by 9.3 for Blueair 511i Max. Intake clearance is on top of that, so measure the gap both ways.
- Blueair Blue Pure 311i Max
- Depends
- Blueair Blue Pure 511i Max
- Depends
I want to run it from another room
Both Blueair 311i Max and Blueair 511i Max support app control, which means this requirement can't separate them. Use the room and placement checks next.
- Blueair Blue Pure 311i Max
- Better fit
- Blueair Blue Pure 511i Max
- Better fit
Ceiling height is ten feet
Lift the ceiling to ten feet while keeping five air changes, and the modeled room areas fall to 340 square feet for Blueair 311i Max and 184 for Blueair 511i Max. That is 20% less floor area than in the eight-foot example, since the purifier has more air to move.
- Blueair Blue Pure 311i Max
- Depends
- Blueair Blue Pure 511i Max
- Depends
In practice
Differences you will notice
Compare room sizes at an equal turnover rate
Blueair 311i Max works out to about 425 square feet and Blueair 511i Max to 230, at five air changes per hour and an eight-foot ceiling.
How we worked this out
Area = CADR × 60 / (ceiling feet × air changes per hour). Inputs are 283 and 153 CFM, 8 feet and 5 changes. Smoke CADR is taken at maximum speed. Real conditions are affected by air mixing, furniture, open doors and filter loading.
Measure the cabinet first, then buy
Blueair 311i Max has a 156.3-square-inch cabinet envelope, compared with 86.5 for Blueair 511i Max. A shallower shape may still need more wall width.
How we worked this out
Width × depth: 12.5 × 12.5 = 156.3 in² and 9.3 × 9.3 = 86.5 in². The cabinet bounding rectangles are measured here, excluding required air clearance.
The gain in pollen is a little more than twofold
On pollen CADR, Blueair lists the 311i Max at 2.10 times the 511i Max.
How we worked this out
365 / 174 = 2.10. For smoke CADR, 283 / 153 = 1.85 times. Each ratio compares the same pollutant on the same maximum-speed basis.
Plug in your numbers
Can either purifier keep up with your room?
This checks hard limits only. Personal preferences are left out of the math.
Blueair Blue Pure 311i Max
Works with your numbers283 CFM of verified clean-air delivery works out to about 7.1 air changes per hour in this room. Hitting the 5 ACH target takes 200 CFM.
Blueair Blue Pure 511i Max
Does not work with your numbers153 CFM of verified clean-air delivery works out to about 3.8 air changes per hour in this room. Hitting the 5 ACH target takes 200 CFM.
This uses each model’s pollutant-specific CADR at top speed and a target of five air changes per hour. Quieter settings clean less air. Raw airflow and one-change coverage claims are never swapped in.
Option A
Blueair, 311i Max
Blue Pure 311i Max
Quiet and smart, this cylinder falls between Blueair's compact 511i and larger 211i and delivers serious smoke airflow given its 12.5-inch base.
- Best for
- Medium rooms that call for strong airflow, a washable fabric prefilter and quiet smart operation
Facts we checked
- Certified CADR is 283 CFM for smoke, 314 for dust and 365 for pollen.
- At 4.8 air changes per hour, Blueair lists 439 square feet.
- The cabinet is 12.5 inches wide, with app and automatic modes, and is rated from 23 to 50 dB.
Option B
Blueair, 511i Max
Blue Pure 511i Max
Very quiet and meant for small rooms, this purifier controls itself effectively, has a washable fabric prefilter and takes up a very small footprint.
- Best for
- Small bedrooms and offices where you'd put low noise, app control and looks ahead of maximum airflow
Facts we checked
- Blueair's listing is 237 square feet at 4.8 air changes per hour.
- Stated sound runs from 19 to 42 dB.
- A washable fabric prefilter wraps around a main filter whose stated service interval is up to nine months.
Spec by spec
Where they really differ
| Spec | Blueair Blue Pure 311i Max | Blueair Blue Pure 511i Max | In practice |
|---|---|---|---|
| Smoke CADR | 283 CFM | 153 CFM | Better to rely on a smoke-specific rate than on a one-air-change marketing room size. |
| Pollen CADR | 365 CFM | 174 CFM | The model that leads on smoke does not necessarily lead on pollen as well. |
| Cabinet width and depth | 12.5 × 12.5 in | 9.3 × 9.3 in | Check both dimensions against the real gap, and keep the clearance the manual calls for around the intakes. |
| Remote app control | Included | Included | Remote schedules matter if the purifier sits far from where you spend your day. |
| Automatic sensor response | Included | Included | Apps and pollution sensors do separate jobs, and a schedule tells you nothing about air quality. |
| Ionizer or electrostatic stage | always-on | always-on | If a purely mechanical filter path is what you want, treat this preference as a firm requirement. |
| Published weight | 7.8 lb | 4.2 lb | A heavy cabinet bothers you less if it stays put than if it must go upstairs every day. |
| Rated power | 32 W | 17 W | Rated input is a comparison of upper limits. Actual consumption shifts with Auto mode and lower fan settings. |
Trade-offs
What each pick costs you
With Blueair Blue Pure 311i Max
- The carbon layer targets lighter household smells and is not meant for lingering solvent or renovation fumes.
With Blueair Blue Pure 511i Max
- Airflow is modest, so large bedrooms won't be covered during serious smoke events.
Decision guide
How to decide
The 311i Max is the choice for a shared room, while the 511i Max fits more easily into a small bedroom where the larger airflow reserve isn't needed.
Ceiling and room size outweigh the model number
At five smoke air changes and eight-foot ceilings, the 311i Max supports about 425 square feet and the 511i Max about 230. When the smaller model fits your room only on a one-change claim, use the larger model.
Don't set sleep noise beside full-speed CADR
Both models list low minimum sound figures, yet maximum CADR isn't delivered at those settings. If you expect useful airflow without running at the loudest setting, a bedroom may need the larger unit.
The pollen gap is wider than the smoke gap
Pollen CFM is 365 for the 311i Max against 174, just over double. Smoke goes up by about 85%, which makes pollen the stronger reason to step up within this pair.
What this page can’t tell you
- CADR is based on the maximum rated fan speed, and minimum noise and maximum airflow occur at different operating points.
- What these calculations compare is particle-cleaning capacity. Nothing in them promises health outcomes or the removal of a specific gas.
By the numbers
What the data shows
What we found across the air purifiers we compare, plus the checked facts behind each finding.
How many fit
Only 14 of the 70 models checked meet every need here: “Wildfire smoke makes its way inside”, “Floor space is very tight for me”, and “I want it to respond automatically”.
14 models fit, out of 70 checkedShow the facts and the math
How we countedThe count uses each product's current fit ratings for “Wildfire smoke makes its way inside”, “Floor space is very tight for me”, and “I want it to respond automatically”. A need with no documented match is not counted.
| Product | Needs it meets | Facts we checked | Sources |
|---|---|---|---|
| Blueair Blue Pure 311i Max |
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| Blueair Blue Pure 511i Max |
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Ready to buy
See today’s price and what owners say
Open either model on Amazon for the current price, customer reviews and delivery options.
Blueair Blue Pure 311i Max
Airflow has to be stronger for a shared room
See price & reviews on AmazonBlueair Blue Pure 511i Max
Only a small corner of floor is free
See price & reviews on AmazonEach link opens in a new tab.
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